For a cyclist who lives in a crowded world where space is at a premium at home and in the workplace, storing a bicycle could present a challenge because of its size. For the same reason, it is often not practical to carry a conventional bicycle on buses, trains, taxis, small boats, and planes, thus limiting its use for the commuting or touring cyclist. Many existing folding bikes are either not full-size bicycles, use very small wheels that compromise stability and comfort, fold into a cumbersome package, or require the use of special components in order to reduce the folded size.
A common folding bicycle design (e.g. Dahon) comprises a single hinge joint on its frame, by which a front half of a bicycle may be folded laterally to meet a rear half, as shown in FIG. 1. Such a folding design with a single frame joint effectively reduces the length of the bicycle by about half when folded. However, the folded bicycle is still too large and cumbersome to carry or store.
In order to reduce the length of the folded bicycle, a second hinge on a frame can be used. This effectively reduces the length to approximately one-third when folded. In another common folding bicycle design (e.g. Brompton), a second hinge joint is located between a rear triangle and a main frame, proximal to the bottom of a seat tube, as shown in FIG. 2 and FIG. 3. The second hinge axis is lateral in orientation, parallel to a wheel axle and transverse to the first hinge. Pivoting a rear wheel assembly longitudinally through approximately 180 degrees about the second hinge brings the rear end of the bicycle to rest below a main tube of a central part of the frame. Pivoting a front wheel assembly laterally about the first hinge through approximately 180 degrees brings the front end of the bicycle to rest alongside the central part of the frame.
A disadvantage of both the aforementioned designs is the predominantly vertical orientation of the axis of the first frame hinge. Natural forces at play during normal riding tend to put much bending stress on the main frame hinge and to unfasten the hinge. Thus a strong clamping means must be used to keep the hinges closed. Over time, the hinge may also develop play in the joint due to the high bending forces on the spindle. Another disadvantage is that folding requires effort to move the front wheel assembly sideways about the first hinge, transversely through a wide angle of approximately 180 degrees. This is a rather unwieldy operation and compromises folding and unfolding time.
Some folding bicycle designs (e.g. Birdy, Mezzo) have tried to overcome the aforesaid problems by doing away with the main frame hinge, and instead use a pivot means at the front fork to fold the front wheel. However, without a hinge on the main frame, the length of the folded bike is longer unless smaller wheels and/or a short main frame are used. Yet a further disadvantage of the above-mentioned designs is that the bicycle cannot be rolled on the ground once it has been fully folded, unless special rollers are fitted, thus adding to the complexity of the design.
It is therefore an object of the present invention to introduce a full-size folding bicycle that can be quickly folded into a compact package for storage in tight spaces and can be readily transported on buses, trains, cars, and boats without compromising stability and comfort.